A stereogram is known as a medium, which can be observed by an observer by changing over a plurality of images depending on the direction of observation. The stereogram widely used at present has a lens array such as lenticular lens, fly-eye lens, etc. arranged on a printing medium.
When this type of stereogram is used, by changing the direction of observation, a plurality of entirely different images can be changed over for observation of an observer. Also, when the stereogram is used, by changing the direction of observation, an image of a 3-dimensional object can be observed from a direction to match the direction of observation. In this case, the observer can observe the 3-dimensional object with stereoscopic effect. Further, when the stereogram is used, by changing the direction of observation, a plurality of images gradually changing can be observed by an observer. In this case, the observer can observe the plurality of changing images as a series of animated images. The display of the changeover of a plurality of images, the display of images with stereoscopic effect, and the display of images with animation effect as described above can be combined together and used at the same time.
In addition to the stereogram, in the Patent Reference 1, a screen is proposed, which comprises a group of pixels, and each pixel is divided to a plurality of regions. Then, different diffraction grating is assigned to each region so that, when it is seen from different directions, different images can be observed as an assembly of diffraction grating regions to project diffracted light in the direction.
[Patent Reference]                Japanese Patent Publication No. 2795698        
[Patent Reference 2]                JP-A-2002-72837        
[Non-Patent Reference 1]                Junpei Tsujiuchi: “Physics Selection 22; Holography”, pp. 33-36 (published by Shokabo Co., Ltd.; Nov. 5, 1997).        
The stereogram comprising a printed matter with a lens array such as lenticular lens, fly-eye lens, etc. as described above requires physical pixel structure (lens array). Thus, it is disadvantageous in that the product has low resolution and is too thick. Also, it requires fine and minute printing and the printing area is limited. In this respect, it is not possible to attain the following two purposes: the improvement of resolution and the increase of number of parallaxes.
According to the patent reference 1, pixels in limited size are cut in each direction of parallax and diffraction grating is assigned and used. This also requires a limited area, and it is not possible to attain the two purposes as given above: the improvement of resolution and the increase of number of parallaxes.
To solve the problems of the prior art as described above, it is an object of the present invention to provide a computer-generated holographic stereogram, which has very high resolution and many numbers of parallaxes.